ECV by dual-energy CT enhances risk stratification in severe aortic stenosis

Introduction Extracellular volume (ECV) reflects diffuse myocardial fibrosis and has been increasingly associated with adverse outcomes in severe aortic stenosis (AS). Dual-energy computed tomography (DECT) technology enables reliable ECV quantification during routine pretranscatheter aortic valve implantation (TAVI) assessment. In this context, we sought to determine the prognostic value of myocardial ECV quantified by DECT, performed as part of the routine pre-TAVI assessment Methods Retrospective cohort of patients with severe AS undergoing pre-TAVI CT (April 2024–April 2025). A delayed dual-energy acquisition was performed for ECV quantification. Global ECV was defined as the mean of basal and mid-ventricular short-axis values. Patients were included irrespective of subsequent management strategy. The primary outcome was all-cause mortality. Secondary outcomes included unplanned cardiovascular hospitalization and urgent aortic valve replacement. Results A total of 248 patients were included (median age 81 years; 49% male). Median follow-up was 11 months [9–15]. Median ECV was 30.4% [27.6–33.7%]. 145 patients underwent valve implantation (136 TAVI, 9 SAVR), and 103 were managed conservatively. ECV did not differ between management strategies (p = 0.118). During follow-up, 20 deaths occurred. Higher ECV was associated with increased all-cause mortality (HR 1.16 per 1% increase; 95% CI 1.07–1.25; p < 0.001) and remained independently predictive after multivariable adjustment (HR 1.15; 95% CI 1.06–1.25; p = 0.001). In a time-dependent Cox model adjusting for AVR as a time-varying covariate, ECV remained independently associated with mortality (p<0.001). Using ROC analysis, the optimal ECV threshold for mortality prediction was 30.05% according to Youden’s index. For clinical applicability, this value was rounded to 30%. Kaplan–Meier estimates demonstrated a 12-month survival of 98.3% (95% CI 95.9–100%) for patients with ECV < 30%, compared with 86.0% (95% CI 79.8–92.7%) for those with ECV ≥ 30% (log-rank p < 0.001). In the time-to-first unplanned cardiovascular hospitalisation analysis, higher ECV was associated with an increased risk of events (HR 1.12 per 1% increase; 95% CI 1.07–1.17; p < 0.0001). This association remained significant after multivariable adjustment (adjusted HR 1.10; 95% CI 1.04–1.17; p = 0.001). Among treated patients, ECV was also higher in those requiring urgent AVR compared with elective procedures (33.9% [31.96–36.35] vs. 29.3% [26.95–31.75]; p < 0.001) and remained independently associated after adjustment (adjusted OR 1.15; 95% CI 1.03–1.30; p = 0.018) Conclusions CT-derived ECV is a marker of adverse prognosis in severe AS. Higher ECV identified patients at increased risk of death, hospitalization, and urgent valve intervention. These findings support the potential role of ECV in routine pre-TAVI evaluation for improved risk stratification.